291621 has 8 divisors (see below), whose sum is σ = 424224. Its totient is φ = 176720.

The previous prime is 291619. The next prime is 291647. The reversal of 291621 is 126192.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 291621 - 2¹ = 291619 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (291661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4386 + ... + 4451.

It is an arithmetic number, because the mean of its divisors is an integer number (53028).

2²⁹¹⁶²¹ is an apocalyptic number.

It is an amenable number.

291621 is a deficient number, since it is larger than the sum of its proper divisors (132603).

291621 is a wasteful number, since it uses less digits than its factorization.

291621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8851.

The product of its digits is 216, while the sum is 21.

The square root of 291621 is about 540.0194440944. The cubic root of 291621 is about 66.3141588028.

Subtracting from 291621 its sum of digits (21), we obtain a square (291600 = 540²).

The spelling of 291621 in words is "two hundred ninety-one thousand, six hundred twenty-one".